I am trying to be as detailed as possible so appologies for this long thread..
A quick summary.
Card will not work by itself on several (AMD and Intel) motherboards with UEFI bios.
Card will work when a second card is installed and boots into Windows on UEFI systems.
Once booted into Windows, can disable the second card and 5970 works perfectly (even in Crossfire with a second 5970) until system is restarted and the whole issue starts again.
It is not a driver issue as this happens before even the bios has loaded and works perfectly once loaded into Windows.
There is no option for enabling PCIE output on the AMD systems as they do not have onboard video.
The card works perfectly on older systems that do not have a UEFI bios.
I have tried several PSU's (Cooler Master V1000 and OCZ ModXstream pro 600w), they all work perfectly on the older motherboards and work fine when doing the "2 card trick".
The diagnostic led on the 5970 is green indicating no issues.
I have asked friends who have 5970's if I could borrow them, I was able to get two others, they all have the same exact issues.
The details are below.
I have a 5970 that I am trying to sell. The card works, however, I can't get it to boot on any system that has an UEFI bios. The system turns on, fans all kick on, but all the USB ports are seemingly dead and the monitor will only display a blank, black screen (not a no signal screen). I did notice on my Sabertooth 990FX that the VGA LED is red, meaning that the board does not think a VGA card is installed but does not do the no vga beep from the speaker.
I have tried several different motherboards and PSUs, the only common thing being the UEFI boards will not boot while the older standard BIOS boards power on and work without issue.
The motherboards I have tried that do not work are (AMD) Asus Sabertooth 990FX R2.0, Asus M5A97, Gigabyte 990FX-UD3, (Intel) Asus P8Z68, Asus P8H77 and an Asus P8H61. Note, none of these AMD motherboards have any type of integrated graphics so that is not the issue. I have also switched out my FX8350 for an FX6300 and a Phenom II 965 on the AMD boards and an Intel i3 3220 and i5 2500k, all these boards have the same issue.
The boards that
do work with the 5970 without any issues are all older (AMD) MSI KA780G, Asrock 770 Extreme 3, (Intel) EVGA 680i SLI, Dell XPS (i7 920) and an Alienware (I7 975).
For the PSU on all of these (except the Alienware) I tried both my Cooler Master V1000 and OCZ ModXStream Pro 600W. So I belive I can rule out both of these PSU's.
On all of the boards that will not boot with this card, if I install another video card (usually a 6670) with the 5970 installed and with the monitor connected to the 5970, it goes to a black screen (like before) but the USB devices will work. Then shortly after the system will boot into windows. I tried the same thing with each card outputting to a monitor. The 5970 will stay black until Windows loads then all is fine, the other card will show the bios splash screen and then the Windows loading screen before loading into Windows.
If that isn't strange enough, once Windows is loaded I can disable the other card used to boot into Windows and use only the 5970 or even dual 5970's. The cards have all passed several hours of stress testing with no issues what-so-ever.
I came across this thread -
http://www.tomshardware.com/answers/id-1710112/sabertoo...
Seems to be the same issue. Works in older systems, does not work in new systems with UEFI motherboard without a second card (I used my 7870XT, 6670 GDDR5 and a 7770).
So after all of this, I am at a loss as on what to do next. I was thinking of maybe installing an updated firmware for the 5970 but I cannot find one for this particular card (OEM ATI/AMD brand). I did however ask around and was able to borrow two other 5970's a HIS 5970 and a Sapphire 5970, these all had the exact same issues as mine. Both of those cards are used in socket 1366 and 1156 i7 builds with a standard bios.
Any help is much appreiciated.